10 mystery birds

I recently acquired 10 mystery birds. They are 6 weeks old and much larger than my BOs the same age. These creatures are so much heavier than the BOs too. They are like little tanks roving around! I am in process of finishing off the coop. I was trying to determine the type and possible sex of these fellows. There are five with larger combs, but I don't know if this determines sex or not. Anyone know what type of bird these are? The birds are white (pardon the dirty birds) with yellow feet.
Thanks,
steven